Newburyport’s significance grew rapidly after the British implemented the Boston Port Act in 1774, closing Boston Harbor in retaliation for the Boston Tea Party. With trade in Boston effectively shut down, Patriot shipping and supply lines were forced to redirect through alternative coastal towns. Newburyport, along with ports like Salem and Gloucester, became a key alternative. The destruction of Portland (then Falmouth, Maine) by British naval forces in October 1775 and blockade of Portsmouth only increased this shift, as merchants and military planners sought safer harbors for operations and commerce.

In addition to maritime contributions, Newburyport served as a supply depot for the Patriot army. The town provided munitions, food, and textiles—key materials for sustaining the war effort. With Boston under British control, Newburyport also functioned as a military and political waypoint, offering a safe route for the movement of troops, leaders, and couriers throughout New England.

In 1775, General George Washington recognized Newburyport’s importance when he authorized local merchant Nathaniel Tracy to procure vessels for Benedict Arnold’s expedition to Quebec. 

To suppress rebellious activities along the New England coast, Lt Henry Mowatt was ordered to undertake punitive missions to “chastise” the seaports from Marblehead, MA to Machias, ME. 

In defense, Newburyport leveraged the mighty Merrimack to their advantage. Difficult to navigate during the best of times, and exacerbated by its brackish muddy water, British sailors, with incomplete charts, would hesitate to enter the mouth of the river. In May of 1776, Newbury and Newburyport voted to erect a fort on Plum Island, with Newburyport voting to spend up to four thousand pounds and Newbury appropriating two hundred pounds for the project. The installation of navigational hazards, possibly crib piers, and cannon off Plum Island and Salisbury Point further helped protect the town from British raids.